Oil and gas wells must normally be cased from the surface location of the wells down to and sometimes through a producing formation. Casing, e.g. steel pipe, is lowered into the wellbore to a desired depth. The space between the casing and the wellbore, i.e. the annulus, is then typically filled with cement. Once the cement sets in the annulus, it holds the casing in place and prevents flow of fluids to or from or between earth formations through which the well passes, e.g. aquifers.
In some wells it is desirable to complete the well as an open hole completion. Generally, this means that the well is not cased through the producing zone or zones. However, the well would normally still be cased and cemented from the surface location down to a depth just above the producing formation. It is desirable not to fill or contaminate the open hole portion of the well with cement during the cementing process. Formation packer shoes have been used to seal the annulus at the lower end of a casing string and circulate cement up the annulus above the packer. Currently available formation packer shoes normally must be drilled out after the cementing operation to provide access to the producing zone below the casing.
A packer cementing shoe disclosed in U.S. Pat. No. 2,925,865 avoids the need to drill out the apparatus after cementing the annulus. It provides an apparatus which sequentially sets a packer, opens a cementing port with a first valve sleeve, closes the cementing port with a second valve sleeve, and finally pumps part of the apparatus used to perform the previous steps out the lower end of the apparatus and into the open hole.